After attending the University of Glasgow, Finlay spent two years studying Roman law at the University of Göttingen but left school in 1823 to follow Lord Byron to Greece. Returning to Scotland briefly to pass his examination in civil law, he again left for Greece in 1825 and remained there the rest of his life.

Although Finlay took part in the war of independence, he lost almost all his possessions after independence was gained; thereafter, he turned from political involvement to farming and the writing of Greek history. He became pessimistic over what he regarded as the new decline of Greece after independence.

Finlay’s works praised the administrative sophistication of the medievalByzantine Empire and provided an innovative emphasis on socioeconomic factors and on the role of the general populace in historical change. His contributions were early recognized by German scholars of Greece, particularly his survey of the Byzantine Empire. His major books are The Hellenic Kingdom and the Greek Nation (1836), Greece Under the Romans, 2 vol. (1844), History of the Byzantine and Greek Empires, 2 vol. (1854), a number of works on Ottoman and Venetian domination in 1856, and History of the Greek Revolution, 2 vol. (1861).